I just received my Arduino Uno WiFi Rev 2 board. When testing some working sketches, I discovered that the delay() function delays roughly only half of the expected time, i.e. an argument of 10000 only delays approx. 5 seconds.
Is this a known issue?
Does the same problem happen if you upload the File > Examples > 01.Basics > Blink sketch?
Yes, I verified that with the 'blink' sketch ...
Which version of Arduino megaAVR Boards are you using? You can check the version in Tools > Board > Boards Manager.
I can tell you that, using Arduino megaAVR Boards 1.6.26 with my Uno WiFi Rev2, the delay timing is correct.
Unfortunately, I don't have an explanation for why yours would be off by half. Hopefully someone else here on the forum with more knowledge on this topic than me will drop in and help out.